Consider the reaction of 2-methyl-1,3-cyclohexadiene with hcl. assuming that the reaction takes place at a very low temperature: (a) draw the intermediate and product structures, including any formal charges

.The product formed in this reaction would be a kinetic product formed from 1,2-addition.

Kindly refer attachments for mechanism and structures of product.

Explanation:

In organic chemistry once the intermediate is generated the reaction can go in two ways. In one way product formed would be rate dependent and would be known as kinetic product and in the other way product formed would be stable and would be know as thermodynamic product.

A kinetic product is formed faster but it is generally not that stable as a thermodynamic product so a kinetic product is formed at lower temperatures where the molecular energy is very less.

A thermodynamic product  formation takes time to form and the reaction is carried out at higher temperatures where the molecules have energy. The thermodynamic product is relatively  stable.

In this case since we are doing our reaction at very low temperature so the major product formed in the reaction would be under kinetic control and hence product formed would be rate dependent.

The reaction of 2-methyl-1,3-cyclohexadiene  with HCl would be a electrophilic addition reaction in which the pi bond would attack HCl to generate a carbocation  intermediate. After the formation of carbocation chloride anion can attack the carbocation and can form the product.

Once the carbocation is formed it can be stabilised by rearrangement or other stabilizing mechanisms.

In this case initially 1-methylcyclohex-2-en-1-ylium carbocation is generated which is at tertiary center as well as allylic position. This carbocation formed initially can stabilize itself through resonance as the charge can be delocalised  with the allyl group.

The reaction can happen in two ways :

In the first way the initially formed 1-methylcyclohex-2-en-1-ylium carbocation is been attacked by the chloride anion and this leads to the 1,2 addition product.

In the other way the initially formed 1-methylcyclohex-2-en-1-ylium carbocation delocalizes its positive charge with the allyl group as it is in conjugation with the allyl group thereby  generating a positive charge at 4 postion and form 3-methylcyclohex-2-en-1-ylium. Now this carbocation is  attacked by the chloride anion and this leads to the 1,4 addition product.

The 1,2 addition product is a Kinetic product as it can quickly lead to products  wheras the 1,4 addition product is a thermodynamic product.

The product formed in this reaction would be a kinetic product formed form 1,2-addition.

Kindly refer the attachments for reaction mechanism.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.